Electrofusion joints have been developed and used for joining pipe used in a variety of applications, such as sewage system piping. Typically, when joining two pipes directly together using an electrofusion joint, one end of a first pipe has a heating element embedded therein. A second pipe is then inserted into the end of the first pipe in which the heating element was embedded. An electric power source supplies an electric current to the heating element embedded in the first pipe. The supply of power to the heating element causes the heating element to produce heat, thereby melting the pipe material in both the first and second pipes in the vicinity of the heating element. The melted pipe material flows together and forms a homogenous joint following a cooling down period, thereby forming a strong joint between the two pipes. The heating element may also be embedded in a fitting, such as a double socket fitting, for joining two pipes through the use of a fitting. Examples of existing electrofusion joints are disclosed in U.S. Pat. No. 3,062,940 to Bauer et al., U.S. Pat. No. 4,530,521 to Nyffeler et al., and U.S. Pat. No. 5,836,621 to Campbell, which are hereby incorporate by reference in their entirety.
When joining pipe using existing electrofusion sockets, the pipe material in the vicinity of the heating element melts and the heating element tends to move or “swim” within the melted pipe material. During such movement, one portion of the heating element may come into contact with another portion causing the circuit to short out. A short circuit causes loss of power to the heating element, thereby prematurely ending formation of the electrofusion joint. This results in a weak joint between the two pipe members. Movement of the heating element becomes more pronounced, and thus a larger problem, with increasing pipe diameter.
In addition, when joining pipe using electrofusion, difficulties are encountered in preparing the pipe for the welding process due to the variation in tolerances encountered in pipe diameters. The variation in pipe diameters may lead to a bell end of a first pipe having an inner diameter too small to receive a second pipe, or, alternatively, the bell end of a first pipe having an inner diameter too large to form a proper fit with the socket end of a second pipe, such that a bad joint is formed. This problem becomes more pronounced as pipe diameters increase since variation in the range of pipe size tolerances increases with pipe diameter.
Thus, there is a continuing need to provide improved assemblies for and methods of making electrofusion joints.